/*
 * buffer.c -- Implementation of functions defined in buffer.h
 *
 * Copyright (C) 2003 Tuukka Karvonen <tkarvone@iki.fi>
 *
 * Version 1.0 October 2003
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

#include "gsm0710_buffer.h"
#include "gsm0710.h"
#include "debug.h"
#include "parameter.h"
#include "timer.h"
#include "usart.h"
#include "stm32f10x_iwdg.h"
//#include <stdlib.h>
//#include <string.h>
//#include <stdio.h>


const unsigned char r_crctable[256] = { //reversed, 8-bit, poly=0x07 
  0x00, 0x91, 0xE3, 0x72, 0x07, 0x96, 0xE4, 0x75, 
  0x0E, 0x9F, 0xED, 0x7C, 0x09, 0x98, 0xEA, 0x7B, 
  0x1C, 0x8D, 0xFF, 0x6E, 0x1B, 0x8A, 0xF8, 0x69, 
  0x12, 0x83, 0xF1, 0x60, 0x15, 0x84, 0xF6, 0x67, 
  0x38, 0xA9, 0xDB, 0x4A, 0x3F, 0xAE, 0xDC, 0x4D, 
  0x36, 0xA7, 0xD5, 0x44, 0x31, 0xA0, 0xD2, 0x43, 
  0x24, 0xB5, 0xC7, 0x56, 0x23, 0xB2, 0xC0, 0x51, 
  0x2A, 0xBB, 0xC9, 0x58, 0x2D, 0xBC, 0xCE, 0x5F, 
  0x70, 0xE1, 0x93, 0x02, 0x77, 0xE6, 0x94, 0x05, 
  0x7E, 0xEF, 0x9D, 0x0C, 0x79, 0xE8, 0x9A, 0x0B, 
  0x6C, 0xFD, 0x8F, 0x1E, 0x6B, 0xFA, 0x88, 0x19, 
  0x62, 0xF3, 0x81, 0x10, 0x65, 0xF4, 0x86, 0x17, 
  0x48, 0xD9, 0xAB, 0x3A, 0x4F, 0xDE, 0xAC, 0x3D, 
  0x46, 0xD7, 0xA5, 0x34, 0x41, 0xD0, 0xA2, 0x33, 
  0x54, 0xC5, 0xB7, 0x26, 0x53, 0xC2, 0xB0, 0x21, 
  0x5A, 0xCB, 0xB9, 0x28, 0x5D, 0xCC, 0xBE, 0x2F, 
  0xE0, 0x71, 0x03, 0x92, 0xE7, 0x76, 0x04, 0x95, 
  0xEE, 0x7F, 0x0D, 0x9C, 0xE9, 0x78, 0x0A, 0x9B, 
  0xFC, 0x6D, 0x1F, 0x8E, 0xFB, 0x6A, 0x18, 0x89, 
  0xF2, 0x63, 0x11, 0x80, 0xF5, 0x64, 0x16, 0x87, 
  0xD8, 0x49, 0x3B, 0xAA, 0xDF, 0x4E, 0x3C, 0xAD, 
  0xD6, 0x47, 0x35, 0xA4, 0xD1, 0x40, 0x32, 0xA3, 
  0xC4, 0x55, 0x27, 0xB6, 0xC3, 0x52, 0x20, 0xB1, 
  0xCA, 0x5B, 0x29, 0xB8, 0xCD, 0x5C, 0x2E, 0xBF, 
  0x90, 0x01, 0x73, 0xE2, 0x97, 0x06, 0x74, 0xE5, 
  0x9E, 0x0F, 0x7D, 0xEC, 0x99, 0x08, 0x7A, 0xEB, 
  0x8C, 0x1D, 0x6F, 0xFE, 0x8B, 0x1A, 0x68, 0xF9, 
  0x82, 0x13, 0x61, 0xF0, 0x85, 0x14, 0x66, 0xF7, 
  0xA8, 0x39, 0x4B, 0xDA, 0xAF, 0x3E, 0x4C, 0xDD, 
  0xA6, 0x37, 0x45, 0xD4, 0xA1, 0x30, 0x42, 0xD3, 
  0xB4, 0x25, 0x57, 0xC6, 0xB3, 0x22, 0x50, 0xC1, 
  0xBA, 0x2B, 0x59, 0xC8, 0xBD, 0x2C, 0x5E, 0xCF };

unsigned char make_fcs(const unsigned char *input, int count) {
  unsigned char fcs = 0xFF;
  int i;
  for (i = 0; i < count; i++) {
    fcs = r_crctable[fcs^input[i]];
  }
  return (0xFF-fcs);
}

typedef enum
{
  csStart = 0,
  csChannel,
  csControl,
  csLength,
  csData,
  csFCS,
  csEnd
} CMUXState;

static GSM0710_Frame GSM_Frame;
static CMUXState csState = csStart;
//static unsigned char frameOK = 0;
static unsigned char currentLength = 0;
static unsigned char fcs = 0xFF;

GSM0710_Frame *GetGSM0710Frame(unsigned char* buffer, unsigned short size, unsigned short timeout)
{
  unsigned short i = 0;
  unsigned char ch;  
  GSM0710_Frame *frame = &GSM_Frame;
  unsigned int start  = GetSysTick();

  while (GetSysTick() - start < timeout)
  {
    IWDG_ReloadCounter();
    if (!GetByte(USART_MODEM, &ch))
      continue;

    //DebugPrintf(DEBUG_LEVEL_OFF, "%02X ", ch);

    switch (csState)
    {
      case csStart:
        if (ch == GSM_F_FLAG)
        {
          csState = csChannel;
          fcs = 0xFF;
        }
        else
        {
          DebugPrintf(DEBUG_LEVEL_INFO, "Drop CMUX Data [%02X]\r\n", ch);
          //DebugPrintf(DEBUG_LEVEL_OFF, "Not start flag\r\n");
          continue;
        }
        break;

      case csChannel:
        if (ch != GSM_F_FLAG)
        {
          csState = csControl;
          frame->channel = ((ch & 252) >> 2);
          fcs = r_crctable[fcs^ch];
        }
        /*else
        {
          DebugPrintf(DEBUG_LEVEL_INFO, "Empty CMUX Frame\r\n");
        }*/
        break;

      case csControl:
        csState = csLength;
        frame->control = ch;
        fcs = r_crctable[fcs^ch];
        break;

      case csLength:
        currentLength = 0;
        frame->data_length = (ch & 254) >> 1;
        DebugPrintf(DEBUG_LEVEL_DETAIL, "Frame Data Length = %d \r\n", frame->data_length);
        fcs = r_crctable[fcs^ch];
        if ((ch & 1) == 0) {
          DebugPrintf(DEBUG_LEVEL_INFO, "Invalid length\r\n");
          csState = csStart;

          //return NULL;
          break;
        }
        if (frame->data_length > 0)
          csState = csData;
        else
          csState = csFCS;

        break;

      case csData:
        if (currentLength < max_frame_size + 1)
        {
          frame->data[currentLength++] = ch;
        }
        else
        {
          DebugPrintf(DEBUG_LEVEL_INFO, "CMUX data too long\r\n");
          csState = csStart;
          break;
        }
        if (currentLength >= frame->data_length)
        {
          csState = csFCS;
        }
        break;

      case csFCS:
        csState = csStart;
        if (frame->data_length > 0) {
      	  if (FRAME_IS(GSM_UI, frame)) {
      	    for (i = 0; i < frame->data_length; i++)
      	      fcs = r_crctable[fcs^(frame->data[i])];
      	  }
        }
        if (r_crctable[fcs^ch] != 0xCF) {
          DebugPrintf(DEBUG_LEVEL_ERR, "Dropping frame: FCS [%02X] doesn't match\r\n", ch);

          //return NULL;
          break;
        }
        else
        {
          //DebugPrintf(DEBUG_LEVEL_OFF, "\r\n");
          return frame;
        }

      case csEnd:
        break;

      default:
        break;
    }
    start  = GetSysTick();
  }

  return NULL;
}

